Hydraulic control device



W. ERNST HYDRAULIC common DEVICE July s, 1937* Filed May 5, 1933 Ill/767970 2 W141. Tfl/VST I? TTOF/Vfrs Patented July 6, 1937 UNITED STATES PATENT OFFICE HYDRAULIC CONTROL DEVICE Walter Ernst, Mount Gilead,v Ohio, assignor, by mesne assignments, to The Hydraulic Press Corporation, Inc., Wilmington, Del., a corporation of Delaware Application May 5, 1933, Serial No. 669,493

6 Claims.

circuit when the pressure in the circuit reaches a predetermined amount.

An object of my invention is to provide a hydraulic control device for regulating a hydraulic circuit, this control device being sensitive to small changes in the volume of the fluid passing 10 through the device.

Another object is to provide a hydraulic device which makes use of an independent differential lifting area to operate the controlling plunger, which area may be of any desired size without being affected by the area required to release the pressure.

Another object is to provide a hydraulic control device wherein the lifting pressure with the plunger valve wide open will be substantially the same as when it is nearly closed, hence providing substantially the same Working pressure for large volumes of motive fluid as for small volumes thereof.

Another object is to provide a hydraulic control device wherein light springs with substantially constant resiliency throughout their range of travel may be used to regulate the plunger, instead of stiff heavy springs which have a variable resilience.

Another object is to provide such a device with a graduated valving of fluid, thereby preventing the noise and vibration occurring when the entire valve area is opened at one time. I

Another object is to provide such a device wherein fluttering or chattering of the plunger valve through rapid reversals of pressure in the line is effectively prevented by causing the plunger lifting to be effected. in a chamber separated from the chamber where the valving action 6 occurs, free backward flow of fluid therebetween being prevented by a retardation device.

Another object is to provide a hydraulic control device which may be used either as an unloader in a hydraulic circuit containing both 5 high pressure and low pressure pumps, or else as a low pressure relief valve in a circuit containing a low pressure pump alone.

Another object is to provide such a device wherein the full pressure is available nearly up to the point of cut-ofi by reason of the valve pressure beingsubstantially independent of the volume of fluid passed through the valve.

Other objects and purposes will be made apparent from the following description taken in 55 connection with the drawing and appended claims.

which the plunger 3 passes.

In the drawing:

Figure 1 is a diagrammatic view of a hydraulic circuit utilizing my hydraulic control device as an unloader to regulate the low pressure and'the high pressure pumps contained in the circuit. 5

Figure 2 is a central vertical section through my hydraulic control device in its preferred form as an unloader.

Figure 3 is a partial central vertical section through my hydraulic control device, showing its 10 preferable modification when used as a low pressure relief valve in a hydraulic circuit containing a low pressure pump.

Figure 4 is a central vertical section through an alternative form of my device adapted for 15 use as a low pressure relief valve.

Figure 5 is a partial vertical section along the line 55 of Figure 2, showing a choke valve in the inlet port of the plunger lifting chamber.

Referringto the drawing in detail, in the hydraulic circuit shown in Figure 1, A is a tank for supplying motive fluid to the circuit, B is a low pressure hydraulic pump of a conventional type, and C is a high pressure hydraulic pump, likewise of a conventional type. D is an external view of my device in use as an unloader between the high pressure and low pressure circuits. E is a high pressure safety valve, F is a check valve per- .mitting unidirectional flow only, G is the hydraulic machine, such as a press, to be operated by the circuit, and H is an operating valve for returning the plunger of the machine G to its raised position after its operation has been completed.

Referring now to the details of my hydraulic control device in its preferred form as an unloader (Figure 2), I is a casing joined to a valve housing 2, as by a threaded connection. Reciprocably mounted partly within the casing I and the'valve housing 2 is a plunger 3 which is free 40 to move up and down against the pressure of a compression spring 4 which makes contact against the head 5 on the plunger 3. The compression spring 4 may be adjusted to any desired pressure by rotating the'adjusting screw 6 which pushes the spring cap 1 downward against the compression spring 4.

The adjustment is maintained in locked position by the lock nut 8. Contained, within the upper part of the valve housing 2 is a plunger lifting chamber 9 through Within this chamber, the plunger diameter is enlarged to form the difierential lifting area In which is of annular form. One side of the plunger lifting chamber 9 has the inlet port ll passing through the-walls of the valve housing 2, where it continues in a conduit I! (Figure 1). v

Passing longitudinally through the plunger 3 is a channel l3 permitting the flow of fluidbetween the interior of the casing l and the exhaust chamber I4 below the end of the plunger 3. The exhaust chamber It continues in an exhaust conduit l5 by which fluid is returned to the tank A. The lower end It of the plunger 3 is tapered as for a purpose which will hereinafter appear. The valve chamber ll of the valve housing 2 is joined on one side by a low pressure feed conduit l8 and on the opposite side by an outlet conduit IS. The inlet port II in the plunger lifting chamber 9 may be equipped with a needle valve, choke valve or other retardation device in order to impede the backward free flow of fluid from the plunger lifting chamber 9, for a purpose which will likewise later appear. One form of this choke valve is shown in Fi ure 5. It consists of a 'conically pointed screw 28 whose threads engage corresponding threads in its housing 29 which is joined to the valve housing 2' by any suitable means such as by the threaded connection 30. The conical tip of the screw 28 partially closes the inlet port H in a manner which may be varied by threading the screw in or out and locking it in place with the lock nut 3|. To one side of the I,

housing 29 is attached the conduit l2.

In the use of my hydraulic control device as an unloader, as shown in Figure 1, the conduit I! V ber a.

A very convenient modification for accomplishing the same purpose in a simpler way is shown in Figure 3, wherein the plunger lifting chamber 9 is connected with the valve chamber I! by a conduit 2| running longitudinally through the plunger 3 and containing the transverse passages 22 and 23 leading into the valve chamber l1 and the plunger lifting chamber}, respectively. A needle or choke valve 24 with a conical point 25 serves toimpede the backward flow of fluid from the plungerliftlng chamber 9 through the conduit 2| into the valve chamber l1, and is adiusted by turning its threaded portion 26 and tightening the lock nut 21. This modification of Figure 3 enables the communication between the plunger lifting chamber 9 and the valve chamber H to be established wholly within the plunger rather than by using external liv as would be required in the form of my device shown in Figure 2 whenused as a low pressure relief valve.

In the operation of my hydraulic control device as an unloader, the device D is arranged as shown in the circuit illustrated in Figure 1, previously described. When the pumps are placed in operation, the low pressure pump B discharges straight through the unloader by way of the low pressure feed conduit It, the valvechamber l1 and the conduit is, thence through thecheck valve F into the ram chamber of the hydraulic press G. When the pressure in the press ram chamber builds up to a certain predetermined amount, as regulated by .the compression force exerted by the compression spring 4, the pressure fluid entering the plunger lifting chamber 9 from the high pressure feed line 20 by way of the conduit It will exert its force against the difierential area ll) of the plunger 3 and lift the plunger. When the plunger rises, it will open communication between the valve chamber I1 and the exprevented from backing into the low pressure line I9 by means of the check valve F. The high pressure continues to act on the differential area "I of the plunger 3 and holds this plunger wide.

open. No power, therefore, is required to bypass the low pressure pump while the high pressure pump is holding pressure.

When it is desired to return the press, the operating valve H is opened, connecting the high pressure feed line 20 with the exhaust line 32, thus by-passing the output of the high pressure pump C, and causing the press ram of the press G to return. a

The presence of the differential area ill on the plunger 3 serves to permit a very slight pressure to lift the plunger. In an ordinary relief valve or unloader where the pressure-works directly against the full area of the plunger and relieves itself by lifting this plunger, the area against which the press will work must always be equal to the area required for the relief, hence requiring a very heavy spring I since the pressure works against the full area of the plunger. Such heavy springs are less resilient than light springs, and have a variable resilience during different-portions of their compression. Consequently, as a,

heavy spring 4 is compressed during travel. of the plunger, its resilience declines and a higher pressureis required to force the plunger upward during the last period of its travel than at the start. The consequence is that the device with a heavy spring 4 will exert a higher regulating pressure with the plunger valve wide open than with the plunger valve almost completely closed: this in turn means that a small volume of liquid passing through this valve will lift the plunger at a lower pressure than a large volume.

Thisdisadvantage is overcome by providing a differential area III for lifting the'plunger 3 instead of allowing the pressure to be exerted required to release the pressure, and an independent differential plunger-lifting area is the result. Consequently, a lighter spring 4 may be used for regulating the operating pressure, such light springs having a greater flexibility and more nearly constant resilience during the period of their travel. This in turn means that the pressm'e required to keep the valve wide open'with a large volume of'liquid passing through thevalve is not substantially diflerent from the pres-' sure required to keep the valve slightly open' when a small volume is passing through it. The full pressure is also available nearly up to the point of cut-oft.

The operation'of the ordinary unloader or relief valve is accompanied by noise and vibration since the entire area of the valve is lifted at once. In my hydraulic control device, however, I have provided the plunger 3 with a tapered end I6. As the plunger rises, the valve will start to open on the high side of the taper and will gradually approach the full opening, thus giving a smooth and graduated cut-off which eliminates such noise and vibration.

In the preferred form of my device, the differential plunger lifting area I9 is placed in a plunger lifting chamber 9 which is separate from the valve chamber l1, and connected therewith by a conduit either having a retarding effect on back flow of liquid by reason of its small diameter or else having a choke valve as previously described. The purpose of this separate chamber for the plunger lifting is to prevent fluttering and chatter of the valve plunger. In the ordinary plunger valve, where the plunger lifting area is in the valve chamber, a drop in pressure occurs when the plunger lifts, this pressure drop immediately producing a re-seating of the valve with a corresponding increase in pressure: this reseating again causes the plunger to lift with a repetition of the pressure drop. Thus the valve plunger will flutter up and down at a high rate because of the rapid reversals of pressure in the hydraulic circuit. In my hydraulic control device,

however, these rapid reversals of pressure in the valve chamber l! are prevented'from reaching the independent plungerlifting chamber 9 because of the choke 'valve therebetween: this choke -valve allows a slow reversal of pressure, but effectively dampens the rapid reversals by obstructing the free backward flow of liquid. The result is that the fluttering is very effectively reduced either completely or to a negligible amount, depending on the adjustment of the choke screws 26 or 28. In small valves the choke screw may be eliminated, a corresponding effect being created by the smallnesslof theconduit connecting the plunger lifting chamber 9 with the valve chamber 11.

In the operation of my hydraulic control device as a low pressure relief valve, but one pressure is present in the hydraulic circuit; as from the low pressure hydraulic pump B. The pressure flows from the pump B through the valve chamber I! of the device into the hydraulic mechanism operated thereby. This pressure also reaches the plunger lifting chamber 9 either through the inlet port H and a conduit connecting it with the valve chamber I! (Figure 2) or else through the drilled conduit 2| in the plunger 3 itself (Figure 3) the latter form of which is especially adapted for use as a relief valve, When the pressure in the circuit builds itself upto a predetermined amount, the pressure in the plunger lifting chamber 9 likewise rises and pushes,

against the differential area I0, causing the plunger to rise against the compression of spring 4 and permitting the liquid entering from the pump B by the conduit l8 to discharge directly into the exhaust conduit l5, thus being by-passed directly without reaching the hydraulic machine being operated.

however, the differential area I 0, on the plunger 3 is in the valve chamber l1, so that the plunger lifting chamber and the valve chamber are combined. This construction eliminates the vibration arising'in types of valves where the plunger. area is acted upon by the pressure, but lacks the further refinement of preventing fluttering through the use of a plunger lifting chamber which is separate from the valve chamber, and with an impedance of free flow of liquid therebetween. The operation of the modification shown in Figure 4 is otherwise essentially the same as that of the types shown in Figures 2 and 3. The requisite pressure acting on the differential area llllifts the plunger, causing the inward flow of fluid through the conduit 18 to baby-passed into the discharge conduit l5 rather than continuing on its way to the hydraulic press or other machine being operated. The modified form of valve in Figure 4, however, likewise has the tapered plunger end l6 which gives a graduated cut-oflf and consequent reduction of noise.

It will be understood that I desire to comprehend within my invention such modifications as may be necessary to adapt it to varying conditionsand uses.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A hydraulic control device comprising a valve chamber, a plunger lifting chamber, an exhaust chamber, a plunger passing reciprocably across said valve chamber to close an outlet port therefrom and extending into said plunger lifting chamber, said plunger havingv a pair of passages therethrough, one passage leading from said valve chamber to said plunger lifting chamber and the other passage leading from said exhaust chamber ,to a chamber other than the aforementioned chambers, said plunger within said plunger lifting chamber having a differential area adapted to cause reciprocation thereof when acted upon by pressure fluid, and means for conducting pressure fluid from said valve chamber to said plunger lifting chamber.

2. A hydraulic control device comprising a valve chamber, a plunger lifting chamber, a

plunger passing reciprocably across said valve chamber to close'an outlet port therefrom and extending into said plunger lifting chamber, said plunger within said plunger lifting chamber having a difierential area adapted to cause reciprocation thereof when acted upon by pressure fluid, and means for admitting pressure fluid to said plunger lifting chamber from said valve chamber, said means comprisinga conduit passing through said plunger between said chambers.

3. A hydraulic control device comprising a valve chamber, an exhaust chamber, a plunger lifting chamber, a plunger passing reciprocably across said plunger lifting chamber to close an outlet port therefrom, said plunger having a differential area adapted to cause reciprocation thereof when acted-upon by' pressure within said plunger lifting chamber, yielding means adapted to resist the motion of said plunger during its reciprocation, and a chamberfor said yielding means, said plunger having a passage leading from said exhaust chamber to said yielding means chamber and an additional passage leading from aid valve chamber to said plunger lifting chamber.

4. A hydraulic control device comprising a valve chamber, an exhaust chamber, a plunger 'lifting chamber, a plunger passing reciprocably across said plunger lifting chamber to close an outlet port therefrom, said plunger having a differential area adapted to cause reciprocation thereof when acted upon by pressure within said chamber, yielding means adapted to resist the motion of-said plunger during its reciprocation, and a chamber for said yielding means, said plunger having a passage leading from said exhaust chamber to said yielding means chamber and an additional passage leading from said chamber to-said plunger lifting chamber, said last-mentioned passage having means for adjustably restricting the flow of fluid therethrough.

5. A hydraulic control device comprising a valve chamber, a plunger-lifting chamber apart therefrom, a valve plunger passing reciprocably across said valve chamber to close an outlet port said plunger to the outlet of said valve and yield ing means for urging said plunger in the opposite direction from the direction of motion caused by the engagement and urge of saidpressure fluid,

whereby to provide substantially the same lifting pressure with the valve plunger wide open as 2 with the valve plunger nearly closed.

6. A hydraulic control device comprising a valve chamber, a plunger-lifting chamber apart therefrom, a valve plunger passing reciprocably across said valve chamber to close an outlet port in the opposite wall thereof, said plunger within said plunger-lifting chamber having a projectingpiston area, said plunger being arranged to be engaged and urged by pressure fluid in its open direction only, means for conducting pressure fluid from said valve chamber to said plungerliftingvchamber, means directly connecting the opposite side of said plunger to the outlet of said valve and yielding means for urging said plunger in its closing direction, whereby to provide substantiallythe same lifting pressure with the valve 

